1. Field of the Invention
This invention relates to peptide analogs that are interleukin-1.beta. protease inhibitors. More particularly, the invention provides a-substituted methyl ketones derived from aspartic acid and the closed hemi-ketal forms thereof as inhibitors of interleukin 1-.beta. protease.
2. Reported Developments
Enzymes involved in the catalytic degradation of proteins by hydrolyzing peptide bonds are known as proteases or proteinases. Proteinases are believed to be involved in various disease states including inflammation, metastasis, tissue damage, bone resorption and muscle degeneration in dystrophic diseases. Proteinases are divided into classes according to their catalytic mechanisms, such as serine-, cystein-, aspartic- and metallo-proteinases. For each class of proteinases, the catalytic site of the enzyme lies in the cleft on the surface of the enzymes in which reside the specificity subsites that bind amino acid side chains and the polypeptide backbone. In designing proteinase inhibitors, it is important to optimize the subsite binding characteristics with appropriate amino acid substrate analogs.
This invention relates to peptide substrates modified with affinity labels that inhibit interleukin-1.beta. protease (hereinafter IL-1.beta. protease). These inhibitors are thought to act by alkylating the cysteine sulfhydryl group (cys 285) within the catalytic site of IL-1.beta. protease. Affinity labeling has been used since the 1960's to prepare irreversible peptide-based inhibitors which act to alkylate the active sites of cysteine proteases. A variety of affinity labels and amino acid sequences have been synthesized to improve the binding of these modified peptide inhibitors to the enzyme's active site. These affinity labels include peptidyl halomethyl ketones, peptidyl diazomethyl ketones, epoxysuccinyl peptides and peptidyl methylsulphonium salts as reviewed by D. Rich in Chapter 4 of "Proteinase Inhibitors", Barret, A. J. and Salvesen, G., eds., Elsevier, 1986. More recently, peptide acyloxymethyl and aryloxymethyl ketons have also been described as affinity lables (Krantz, A. et al, Biochemisty, 30, p. 4678-4687, 1991). Current research (see for example European Patent Application, Pub. No. 015,748 A2; PCT International Publication No. WO 91/15577; Chapman, K. T., Biorganic & Medicinal Chem. Lett. 1992, 2, 613-618) has been directed towards understanding the enzyme binding specificity requirements in designing novel small molecular weight protease inhibitors that are efficacious, safe and have specificity for IL-1.beta. protease which is believed to play an important role in many disease states (see Epstein, F. H., New Engl. Jrl. of Med., 328, p. 106-113, 1993).
Disease states in which IL-1.beta. protease inhibitors may be useful as therapeutic agents include: infectious diseases, such as meningitis and salpingitis; septic shock, respiratory diseases; inflammatory conditions, such as arthritis, cholangitis, colitis, encephalitis, endocerolits, hepatitis, pancreatitis and reperfusion injury, immune-based diseases, such as hypersensitivity, auto-immune diseases, such as multiple sclerosis; bone diseases; and certain tumors.
The following publications illustrate that IL-1.beta. inhibitors and antagonists are useful in modifying certain disease states in vivo.
1) IL-1 is present in affected tissues in ulcerative colitis in humans. In animal models of the disease, IL-1.beta. levels correlate with severity. In the model, administraton of IL-1ra reduced tissue necros and the number of inflammatory cells in the colon. Cominelli, F., Nast, C. C, Clark, B. D., Schindler, R., Llerena, R., Eysselein, V. E., Thompson, R. C., and Dinarello, C. A "Interleukin-1 gene expression, synthesis, and effect of cic IL-1 receptor blocke in rabbit immune complex colitis" J. Clin. Investigations (1990) Vol. 86, pp, 972-980.
2) IL-1ra supresses joint swelling in the PG-APS model of arthritis in rats. Schwab, J. H., Anderle, S. K., Brown, R. R., Dalldorf, F. G. and Thompson, R. C. "Pro- and Anti-Inflammatory Roles of Interelukin-1 in Recurrence of Bacterial Cell Wall-Induced Arthritis in Rats". Infect. Immun. (1991) 59; 4436-4442.
3) IL-1ra shows efficacy in an small open-label human RA trial. Lebsack, M. E., Paul, C. C., Bloedow, C. C., Burch, F. X., Sack, M. A., Chase, W., and Catalano, M. A. "Subcutaneous IL-1 Receptor Antagonist in Patients with Rheumatoid Arthritis" Arth. Rheum. (1991) 34; 545.
4) IL-1 appears to be an autocrine growth factor for the proliferation of CML cells. Both IL-1ra and sIL-1R inhibit colony growth in cells removed from leukemia patients. Estrov, Z., Kurzrock, R., Wetzler, M., Kantarjian, H., Blake, M., Harris, D., Gutterman, J. U., and Talpaz, M. "Supression of chronic myelogenous leukemia colony growth by interleukin-1 (IL-1) receptor antagonist and soluble IL-1 receptors: a novel application for inhibitors of IL-1 activity". Blood (1991) 78; 1476-1484.
5) As in 4) above, but for acute myclogenous leukemia rather than chronic myelogenous leukemia. Estrov, Z., Kurzrock, R., Estey, E., Wetzler, M., Ferrajoli, A., Harris, D., Blake, M. Guttermann, J. U., and Talpaz, M. "Inhibition of acute myelogenous leukemia blast proliferation by interleuldn-1 (IL-1) receptor antagonist and soluble IL-1 receptors". (1992) Blood 72, 1938-1945.
It is an object of the present invention to provide novel peptidyl substrate analogs modified with electronegative leaving groups that bind at the active site of IL-1.beta. protease and inhibit IL-1.beta. protease activity. IL-1.beta. protease cleaves a biologically inactive 34 kD precursor of IL-1.beta. to form the biologically active 17 kD cytokine. This cleavage occurs at the peptidyl sequence of Val-His-Asp/-Ala-Pro-Val.
It is another object of the present invention to provide compositions comprising the above-referred to compounds.
It is a further object of the present invention to provide a method of use of the composition for the treatment of the above-identified disease states.